Nonlinear aeroelastic analysis of a morphing flap

A morphing flap integrated with an actuation mechanism was designed and investigated. Based on structure parameters from static experiments, a finite element model of the flap was created within MSC Patran software. Normal modal analysis and linear flutter analysis were carried out firstly. Vg and Vf curves were obtained to determine the critical flutter speeds with and without the actuation mechanism. Structural mass, damping, stiffness, and aerodynamic matrixes were printed with DMAP language to form an aeroelastic equation in modal coordinate. The freeplay nonlinearity between disks attached to the curved beams and wing skins was considered in the aeroelastic analysis. An unsteady aerodynamic influence coefficients matrix was calculated by Roger's approximation. The nonlinear aeroelastic equation in modal coordinate was solved by an iterative program written with MATLAB software. Based on the reduced-order aeroelastic model, the effect of freeplay on aeroelastic responses was investigated. Numerical results show that the freeplay nonlinearity may reduce critical flutter speed, leading to supercritical Hopf bifurcation.